/*
 * StringReader.java - ScriptME
 * 
 * Copyright (c) 2009 Cesar Henriques <cesar at alttab.com.ar>.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the GNU Lesser Public License v2.1
 * which accompanies this distribution, and is available at
 * http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 * 
 * Based on FESI Project
 * 
 * Contributors:
 * 	Jean-Marc Lugrin - initial API and implementation
 * 	Cesar Henriques <cesar at alttab.com.ar> - J2ME Porting and Extensions
 */
package org.scriptme.util;

import java.io.*;

/**
 * A character stream whose source is a string.
 * 
 * @version 1.15, 00/02/02
 * @author Mark Reinhold
 * @since JDK1.1
 */
public class StringReader extends Reader {

	/** The str. */
	private String str;

	/** The length. */
	private int length;

	/** The next. */
	private int next = 0;

	/** The mark. */
	private int mark = 0;

	/**
	 * Create a new string reader.
	 * 
	 * @param s
	 *            String providing the character stream.
	 */
	public StringReader(String s) {
		this.str = s;
		this.length = s.length();
	}

	/**
	 * Check to make sure that the stream has not been closed.
	 * 
	 * @throws IOException
	 *             Signals that an I/O exception has occurred.
	 */
	private void ensureOpen() throws IOException {
		if (str == null)
			throw new IOException("Stream closed");
	}

	/**
	 * Read a single character.
	 * 
	 * @return The character read, or -1 if the end of the stream has been
	 *         reached
	 * 
	 * @throws IOException
	 *             Signals that an I/O exception has occurred.
	 * 
	 * @exception IOException
	 *                If an I/O error occurs
	 */
	public int read() throws IOException {
		synchronized (lock) {
			ensureOpen();
			if (next >= length)
				return -1;
			return str.charAt(next++);
		}
	}

	/**
	 * Read characters into a portion of an array.
	 * 
	 * @param cbuf
	 *            the cbuf
	 * @param off
	 *            the off
	 * @param len
	 *            the len
	 * 
	 * @return The number of characters read, or -1 if the end of the stream has
	 *         been reached
	 * 
	 * @throws IOException
	 *             Signals that an I/O exception has occurred.
	 * 
	 * @exception IOException
	 *                If an I/O error occurs
	 */
	public int read(char cbuf[], int off, int len) throws IOException {
		synchronized (lock) {
			ensureOpen();
			if ((off < 0) || (off > cbuf.length) || (len < 0)
					|| ((off + len) > cbuf.length) || ((off + len) < 0)) {
				throw new IndexOutOfBoundsException();
			} else if (len == 0) {
				return 0;
			}
			if (next >= length)
				return -1;
			int n = Math.min(length - next, len);
			str.getChars(next, next + n, cbuf, off);
			next += n;
			return n;
		}
	}

	/**
	 * Skip characters.
	 * 
	 * @param ns
	 *            the ns
	 * 
	 * @return the long
	 * 
	 * @throws IOException
	 *             Signals that an I/O exception has occurred.
	 * 
	 * @exception IOException
	 *                If an I/O error occurs
	 */
	public long skip(long ns) throws IOException {
		synchronized (lock) {
			ensureOpen();
			if (next >= length)
				return 0;
			long n = Math.min(length - next, ns);
			next += n;
			return n;
		}
	}

	/**
	 * Tell whether this stream is ready to be read.
	 * 
	 * @return True if the next read() is guaranteed not to block for input
	 * 
	 * @throws IOException
	 *             Signals that an I/O exception has occurred.
	 * 
	 * @exception IOException
	 *                If the stream is closed
	 */
	public boolean ready() throws IOException {
		synchronized (lock) {
			ensureOpen();
			return true;
		}
	}

	/**
	 * Tell whether this stream supports the mark() operation, which it does.
	 * 
	 * @return true, if mark supported
	 */
	public boolean markSupported() {
		return true;
	}

	/**
	 * Mark the present position in the stream. Subsequent calls to reset() will
	 * reposition the stream to this point.
	 * 
	 * @param readAheadLimit
	 *            the read ahead limit
	 * 
	 * @throws IOException
	 *             Signals that an I/O exception has occurred.
	 * 
	 * @exception IllegalArgumentException
	 *                If readAheadLimit is < 0
	 * @exception IOException
	 *                If an I/O error occurs
	 */
	public void mark(int readAheadLimit) throws IOException {
		if (readAheadLimit < 0) {
			throw new IllegalArgumentException("Read-ahead limit < 0");
		}
		synchronized (lock) {
			ensureOpen();
			mark = next;
		}
	}

	/**
	 * Reset the stream to the most recent mark, or to the beginning of the
	 * string if it has never been marked.
	 * 
	 * @throws IOException
	 *             Signals that an I/O exception has occurred.
	 * 
	 * @exception IOException
	 *                If an I/O error occurs
	 */
	public void reset() throws IOException {
		synchronized (lock) {
			ensureOpen();
			next = mark;
		}
	}

	/**
	 * Close the stream.
	 */
	public void close() {
		str = null;
	}
}
